Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description discloses a filtering behavior: it only lists models that have per-model UK repair prices, not all car models. However, with no annotations and no output schema, it does not state return format, ordering, pagination, or whether the output can be used as input to sibling tools. The disclosure is minimal but non-contradictory.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

One sentence with no filler. The condition 'has per-model UK repair prices for' is front-loaded and immediately clarifies scope. It is appropriately concise.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-param listing tool with no output schema, the description conveys the core purpose and filtering condition. It is somewhat sparse about the nature of the returned model list (e.g., whether it returns identifiers suitable for downstream calls), but given the simplicity, it is largely complete. The absence of links to sibling tools is a minor gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has zero parameters, so the description needs no parameter guidance. The baseline for 0-param tools is 4; the description does not need to add parameter semantics.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb 'List' with a clear resource 'car models' and a scope condition ('has per-model UK repair prices for'). This differentiates it from siblings like list_repairs and get_model_costs, which list repairs or fetch costs respectively. The purpose is immediately understandable.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this tool versus alternatives is provided. It does not mention that this is the discovery step before calling get_model_costs or get_repair_cost, nor does it state any exclusions. An agent is left to infer from the tool name and sibling names.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.